U0100 on Toyota
Lost Communication with ECM/PCM
U0100 on Toyota vehicles indicates lost communication with ecm/pcm. Au7o has documented this code across 1 Toyota model — most commonly on Matrix. U0100 is a network communication code meaning a module has lost communication with the engine control module / powertrain control module (ECM/PCM) over the vehicle's data bus. The ECM/PCM is the brain that runs the engine, so when other modules can no longer 'talk' to it, the effects can be serious — a no-start, stalling, multiple warning lights, and many other modules logging faults at once. This is almost always a wiring, connector, power/ground, or bus fault, or a failure of the ECM/PCM itself, rather than a single sensor. It should be diagnosed promptly because the vehicle may be undrivable.
Common Causes of U0100
- •Loss of power or ground to the ECM/PCM
- •CAN bus wiring damage, short, or open circuit
- •Corroded, loose, or damaged connectors at the module
- •Blown fuse feeding the ECM/PCM
- •Failed ECM/PCM
- •Another faulty module pulling down the data bus
- •Water intrusion or corrosion in a connector/harness
U0100 on Toyota by Model
Toyota Matrix(1 issue)
- Engine Control Module Solder/Varistor Cracking Causing Stalling and Harsh Shifting (Recall 10V384)2005-2008
Toyota recalled roughly 1.13 million 2005-2008 Corolla and Corolla Matrix vehicles built with the 1ZZ-FE engine and two-wheel drive because the engine control module was improperly manufactured. Cracks can develop at solder points or on varistors on the ECM circuit board. Symptoms escalate from an illuminated check engine light to abnormally harsh automatic transmission shifting, a no-start condition, and in the worst case the engine shutting off while the vehicle is being driven. Toyota's internal campaign designation is A0J. Owners of 2004 cars report the same failure pattern with a mechanically similar module even though that year sits outside the recall population, so a 2004 with these symptoms should still have the ECM considered. Note the recall is limited to 2WD 1ZZ-FE cars - AWD and XRS models were built with different modules.
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View U0100 across all makes →Frequently Asked Questions
What does U0100 mean on Toyota?▼
U0100 stands for "Lost Communication with ECM/PCM." U0100 is a network communication code meaning a module has lost communication with the engine control module / powertrain control module (ECM/PCM) over the vehicle's data bus. The ECM/PCM is the brain that runs the engine, so when other modules can no longer 'talk' to it, the effects can be serious — a no-start, stalling, multiple warning lights, and many other modules logging faults at once. This is almost always a wiring, connector, power/ground, or bus fault, or a failure of the ECM/PCM itself, rather than a single sensor. It should be diagnosed promptly because the vehicle may be undrivable. On Toyota specifically, this code is documented across 1 model.
What causes U0100 on Toyota vehicles?▼
Common causes on Toyota: Loss of power or ground to the ECM/PCM, CAN bus wiring damage, short, or open circuit, Corroded, loose, or damaged connectors at the module, Blown fuse feeding the ECM/PCM, Failed ECM/PCM. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix U0100 on a Toyota?▼
Repair costs vary widely depending on the root cause and specific Toyota model.
Which Toyota models have U0100 documented?▼
Au7o has documented U0100 on 1 Toyota model: Matrix.